CVE-2026-98096 (GCVE-0-2026-98096)

Vulnerability from cvelistv5 – Published: 2026-09-25 10:24 – Updated: 2026-09-25 14:42
VLAI
Title
ipv6: sr: restore network header before routing and forwarding
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: sr: restore network header before routing and forwarding ipv6_srh_rcv() runs with skb->data at the Segment Routing Header (SRH) while skb_network_header() points at the IPv6 header. When segments_left > 0, ipv6_srh_rcv() previously restored the skb->data position by pushing sizeof(struct ipv6hdr), assuming the SRH immediately followed the fixed IPv6 header. If another extension header (such as a Hop-by-Hop options header) precedes the SRH, skb_network_offset() remained negative. This led to two problems: 1. During ip6_route_input(), fib6_rules_early_flow_dissect() invokes __skb_flow_dissect() which passes the negative skb_network_offset() to flow dissection, breaking BPF and C flow dissector logic. 2. If forwarded via ip6_forward() or redirected via act_mirred, downstream handlers (like sch_fragment() or neighbour output) pass the negative offset as an unsigned length, triggering OOB memcpy or buffer overflows. Fix this by pushing -skb_network_offset(skb) before routing, ensuring skb_network_offset(skb) is 0 for route lookup / flow dissection as well as downstream forwarding. On the loopback path, pull skb_transport_offset(skb) to restore skb->data to the SRH before looping back.
Severity
7.4 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1ababeba4a21f3dba3da3523c670b207fb2feb62 , < ce4c8beedc19aceeab0e7bdc6f34394fb158c47c (git)
Affected: 1ababeba4a21f3dba3da3523c670b207fb2feb62 , < 97b21ef57dfabbff660a4672c9fef7edfb720f47 (git)
Affected: 1ababeba4a21f3dba3da3523c670b207fb2feb62 , < 3ad7dca5e03bd64c65983a19734337512fd75491 (git)
Affected: 1ababeba4a21f3dba3da3523c670b207fb2feb62 , < 975b5b067f525a1b1338c4a3bee1c46545801518 (git)
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Linux Linux Affected: 4.10
Unaffected: 0 , < 4.10 (semver)
Unaffected: 6.12.111 , ≤ 6.12.* (semver)
Unaffected: 6.18.53 , ≤ 6.18.* (semver)
Unaffected: 7.2.7 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/exthdrs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "ce4c8beedc19aceeab0e7bdc6f34394fb158c47c",
              "status": "affected",
              "version": "1ababeba4a21f3dba3da3523c670b207fb2feb62",
              "versionType": "git"
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              "version": "1ababeba4a21f3dba3da3523c670b207fb2feb62",
              "versionType": "git"
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              "version": "1ababeba4a21f3dba3da3523c670b207fb2feb62",
              "versionType": "git"
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              "versionType": "git"
            }
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        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/exthdrs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.10"
            },
            {
              "lessThan": "4.10",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.111",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.53",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.111",
                  "versionStartIncluding": "4.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.53",
                  "versionStartIncluding": "4.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.7",
                  "versionStartIncluding": "4.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc2",
                  "versionStartIncluding": "4.10",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: sr: restore network header before routing and forwarding\n\nipv6_srh_rcv() runs with skb-\u003edata at the Segment Routing Header (SRH)\nwhile skb_network_header() points at the IPv6 header.\n\nWhen segments_left \u003e 0, ipv6_srh_rcv() previously restored the skb-\u003edata\nposition by pushing sizeof(struct ipv6hdr), assuming the SRH immediately\nfollowed the fixed IPv6 header. If another extension header (such as a\nHop-by-Hop options header) precedes the SRH, skb_network_offset()\nremained negative.\n\nThis led to two problems:\n1. During ip6_route_input(), fib6_rules_early_flow_dissect() invokes\n   __skb_flow_dissect() which passes the negative skb_network_offset()\n   to flow dissection, breaking BPF and C flow dissector logic.\n2. If forwarded via ip6_forward() or redirected via act_mirred, downstream\n   handlers (like sch_fragment() or neighbour output) pass the negative\n   offset as an unsigned length, triggering OOB memcpy or buffer overflows.\n\nFix this by pushing -skb_network_offset(skb) before routing, ensuring\nskb_network_offset(skb) is 0 for route lookup / flow dissection as well as\ndownstream forwarding. On the loopback path, pull skb_transport_offset(skb)\nto restore skb-\u003edata to the SRH before looping back."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.4,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The bad input is a routed IPv6 packet sent by a remote host: a Hop-by-Hop header followed by an SRH with segments_left\u003e0. ipv6_srh_rcv() processes it on receive, and its fixed skb_push(sizeof(struct ipv6hdr)) leaves skb_network_offset() negative before ip6_route_input() and dst_input() forward the packet.\nAC:H - ipv6_srh_rcv() drops the packet unless seg6_enabled, which defaults to 0, is set both in devconf_all and on the ingress interface. The out-of-bounds memcpy in sch_frag_prepare_frag() also needs the admin to have set up tc act_ct with an MRU plus act_mirred on the forwarding path. The remote attacker cannot set up either of these.\nPR:N - No authentication is needed to send the packet. seg6_hmac_validate_skb() accepts SRHs that carry no HMAC TLV when seg6_require_hmac is at its default of 0, so an unauthenticated sender reaches the segments_left\u003e0 branch.\nUI:N - No victim action is needed. The router processes the attacker\u0027s SRH packet in softirq receive context as soon as it arrives.\nS:U - The corruption stays inside the router\u0027s own kernel (skb metadata, then the per-CPU sch_frag_data_storage and memory after it). No VM, IOMMU or sandbox boundary is crossed.\nC:N - With the negative offset, the flow dissector and the neighbour output path read or write inside the skb head, and the bytes sch_frag reads out of bounds go into per-CPU storage. I found no path that sends kernel memory back to the attacker.\nI:H - sch_frag_prepare_frag() takes the negative skb_network_offset() as unsigned hlen and runs memcpy(\u0026data-\u003el2_data, skb-\u003edata, hlen). That writes packet bytes the attacker supplied past the per-CPU sch_frag_data_storage buffer, an out-of-bounds kernel write.\nA:H - The roughly 4 GB memcpy in sch_frag_prepare_frag() will fault and crash the router. On other paths the negative offset breaks flow dissection and garbles forwarded packets. The attacker can repeat this with each crafted packet."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-25T14:42:04.399Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ce4c8beedc19aceeab0e7bdc6f34394fb158c47c"
        },
        {
          "url": "https://git.kernel.org/stable/c/97b21ef57dfabbff660a4672c9fef7edfb720f47"
        },
        {
          "url": "https://git.kernel.org/stable/c/3ad7dca5e03bd64c65983a19734337512fd75491"
        },
        {
          "url": "https://git.kernel.org/stable/c/975b5b067f525a1b1338c4a3bee1c46545801518"
        }
      ],
      "title": "ipv6: sr: restore network header before routing and forwarding",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98096",
    "datePublished": "2026-09-25T10:24:27.098Z",
    "dateReserved": "2026-09-25T10:19:56.076Z",
    "dateUpdated": "2026-09-25T14:42:04.399Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "net/ipv6/exthdrs.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "lessThan": "ce4c8beedc19aceeab0e7bdc6f34394fb158c47c",
                    "status": "affected",
                    "version": "1ababeba4a21f3dba3da3523c670b207fb2feb62",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "97b21ef57dfabbff660a4672c9fef7edfb720f47",
                    "status": "affected",
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                    "versionType": "git"
                  },
                  {
                    "lessThan": "3ad7dca5e03bd64c65983a19734337512fd75491",
                    "status": "affected",
                    "version": "1ababeba4a21f3dba3da3523c670b207fb2feb62",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "975b5b067f525a1b1338c4a3bee1c46545801518",
                    "status": "affected",
                    "version": "1ababeba4a21f3dba3da3523c670b207fb2feb62",
                    "versionType": "git"
                  }
                ]
              },
              {
                "defaultStatus": "affected",
                "product": "Linux",
                "programFiles": [
                  "net/ipv6/exthdrs.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "status": "affected",
                    "version": "4.10"
                  },
                  {
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                    "status": "unaffected",
                    "version": "0",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "6.12.*",
                    "status": "unaffected",
                    "version": "6.12.111",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "6.18.*",
                    "status": "unaffected",
                    "version": "6.18.53",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "7.2.*",
                    "status": "unaffected",
                    "version": "7.2.7",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "*",
                    "status": "unaffected",
                    "version": "7.3-rc2",
                    "versionType": "original_commit_for_fix"
                  }
                ]
              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: sr: restore network header before routing and forwarding\n\nipv6_srh_rcv() runs with skb-\u003edata at the Segment Routing Header (SRH)\nwhile skb_network_header() points at the IPv6 header.\n\nWhen segments_left \u003e 0, ipv6_srh_rcv() previously restored the skb-\u003edata\nposition by pushing sizeof(struct ipv6hdr), assuming the SRH immediately\nfollowed the fixed IPv6 header. If another extension header (such as a\nHop-by-Hop options header) precedes the SRH, skb_network_offset()\nremained negative.\n\nThis led to two problems:\n1. During ip6_route_input(), fib6_rules_early_flow_dissect() invokes\n   __skb_flow_dissect() which passes the negative skb_network_offset()\n   to flow dissection, breaking BPF and C flow dissector logic.\n2. If forwarded via ip6_forward() or redirected via act_mirred, downstream\n   handlers (like sch_fragment() or neighbour output) pass the negative\n   offset as an unsigned length, triggering OOB memcpy or buffer overflows.\n\nFix this by pushing -skb_network_offset(skb) before routing, ensuring\nskb_network_offset(skb) is 0 for route lookup / flow dissection as well as\ndownstream forwarding. On the loopback path, pull skb_transport_offset(skb)\nto restore skb-\u003edata to the SRH before looping back."
          }
        ],
        "id": "CVE-2026-98096",
        "lastModified": "2026-09-25T15:18:05.827",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "HIGH",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 7.4,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "NONE",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 2.2,
              "impactScore": 5.2,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-09-25T11:17:39.373",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/3ad7dca5e03bd64c65983a19734337512fd75491"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/975b5b067f525a1b1338c4a3bee1c46545801518"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/97b21ef57dfabbff660a4672c9fef7edfb720f47"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/ce4c8beedc19aceeab0e7bdc6f34394fb158c47c"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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